High-Speed Helicopter Revolution: Sikorsky's Dual-Rotor Design

Helicopters have always had a hard time going fast. The forward motion of the chopper adds airspeed to advancing blades, while simultaneously reducing the speed of retreating blades. So, at high speeds one blade risks going supersonic as it gains lift, while a blade on the other side teeters on the edge of a stall.

Hoping to overcome that problem, Sikorsky Aircraft is testing a helicopter that uses two sets of blades that spin in opposite directions, balancing out the loss of lift experienced by the retreating blades on each side. The system is part of a suite of advances that Sikorsky Aircraft calls X2 Technology, which should allow the test vehicle to achieve nearly twice the speed of a conventional helicopter. "We're designing for a cruise speed of 288 mph," says program manager Peter Grant, "with dash speeds much greater than that." Theoretically, an X2-equipped chopper could hit 334 mph.

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The 30-ft.-long X2 Technology Demonstrator is a research platform, so it won't directly spawn any production helicopters. Whether the technology eventually winds up in everything from gunships to civilian transports, such as Sikorsky's "Commercial Intermediate" concept (illustrated above), may depend on how well the testbed flies. At press time Sikorsky had yet to set a flight testing date.